In a typical irrigation system a manually programmable electronic controller selectively energizes a solenoid operated valve to cause pressurized water to be delivered to a set of sprinklers connected to a common buried PVC pipe. Each set of sprinklers is referred to as a station or zone and is supplied with pressurized water by a corresponding solenoid actuated valve. The solenoid actuated valve typically has a clam shell or bonnet configuration exemplified in U.S. Pat. No. 6,079,437 granted Jun. 27, 2000 to Beutler et al. and assigned to Hunter Industries, Inc. In a bonnet valve, pressurized upstream or inlet water passes via a small metering orifice in a central metering body to a control chamber inside the upper clam shell on the back side of a circular elastomeric diaphragm to apply a closing pressure. This forces the periphery of a valve member connected to the diaphragm against a valve seat. Water can be vented from the control chamber through a small pilot valve passage which is opened by a solenoid actuated pilot valve, which causes the diaphragm and valve member to move upwardly and allow water to flow freely through the main flow passage of the valve.
Another type of valve used in industrial and agricultural applications, but not in residential and commercial irrigation systems, is known as a sleeve valve and is exemplified in U.S. Pat. No. 5,671,774 granted Sep. 30, 1997 to Klein et al. and assigned to Nelson Irrigation Corporation. In a sleeve valve, a substantially cylindrical elastomeric sleeve is surrounded by an outer cylindrical rigid housing to define a control chamber between the elastomeric sleeve and housing. The ends of the elastomeric sleeve overlap a mandrel including opposing frusto-conical sections having circumferentially spaced slots. A solenoid operated pilot valve can release pressurized water from a control chamber to allow the elastomeric sleeve to expand and uncover the slots, thereby allowing water to flow freely through the main flow passage of the sleeve valve.
A two-way solenoid actuated pilot valve typically includes a solenoid whose spring biased plunger moves an elastomeric seal. When the solenoid is de-energized the plunger pushes the elastomeric seal against a pilot valve seat in a pilot valve chamber, closing a passage that leads from the control chamber of the main valve. This closes the main valve. When the solenoid is energized, the plunger retracts and the elastomeric seal moves away from the pilot valve seat, allowing pressurized liquid to leave the control chamber through the passage, through the pilot valve chamber and through a relief passage into the outlet of the main valve. This opens the main valve. See U.S. Pat. No. 5,979,482 granted Nov. 9, 1999 to Scott and assigned to Hunter Industries, Inc.
A three-way solenoid actuated pilot valve is used to switch between two different sources and a common destination, and vice versa. An elastomeric seal is moved against a first pilot valve seat when the plunger is retracted and against a second pilot valve seat when the plunger is extended. Valves used in residential and commercial irrigation systems have used three way solenoid actuated pilot valves. The power supplied to solenoid actuated valves used in residential and commercial irrigation systems is relatively low. This necessitates the use of relatively small pins and seals in three way solenoid actuated pilot valves that are expensive to manufacture and assemble. These delicate components require significant precision for reliable operation and they are prone to breakage.